Direct bilirubin is associated with low-density lipoprotein subfractions and particle size in overweight and centrally obese women

The association between bilirubin levels, and the incidence of metabolic syndrome and diabetes mellitus: a systematic review and meta-analysis of cohort studies

OBJECTIVES

The objective of this meta-analysis was to investigate the association between plasma bilirubin levels and the incidence of metabolic syndrome and diabetes mellitus across all populations.

METHODS

Several databases were searched, including PubMed (Medline), Scopus, Web of Science, and Embase (Elsevier), to identify relevant cohort studies. All cohort studies that reported the risk ratio along with a 95% confidence interval were included. The association between bilirubin levels and metabolic syndrome or diabetes was reported as a pooled RR with a 95% CI in the forest plot. All analyses were conducted using STATA version 17, with a significance level of 0.05.

RESULTS

Out of the 10 studies included in the analysis, four investigated the effect of hyperbilirubinemia on the incidence of type 2 diabetes. When these four studies were combined, the pooled RR was 0.78 (95% CI: 0.73, 0.83; I2: 88.61%; P heterogeneity <  0.001), indicating a significant association between hyperbilirubinemia and decreased risk of type 2 diabetes. Five of the 10 studies evaluated the effect of hyperbilirubinemia on the incidence of metabolic syndrome, and the pooled RR was 0.70 (95% CI: 0.67, 0.73; I2: 78.13%; P heterogeneity <  0.001), indicating a significant association between hyperbilirubinemia and decreased risk of metabolic syndrome.

CONCLUSION

The findings suggest that elevated levels of bilirubin may have a significant protective effect against the development of diabetes mellitus and metabolic syndrome.

Activation of the Nrf-2/HO-1 signalling axis can alleviate metabolic syndrome in cardiovascular disease

Background: Cardiovascular disease (CVD) is widely observed in modern society. CVDs are responsible for the majority of fatalities, with heart attacks and strokes accounting for approximately 80% of these cases. Furthermore, a significant proportion of these deaths, precisely one-third, occurs in individuals under 70. Metabolic syndrome encompasses a range of diseases characterized by various physiological dysfunctions. These include increased inflammation in adipose tissue, enhanced cholesterol synthesis in the liver, impaired insulin secretion, insulin resistance, compromised vascular tone and integrity, endothelial dysfunction, and atheroma formation. These factors contribute to the development of metabolic disorders and significantly increase the likelihood of experiencing cardiovascular complications.Method: We selected studies that proposed hypotheses regarding metabolic disease syndrome and cardiovascular disease (CVD) and the role of Nrf2/HO-1 and factor regulation in CVD research investigations based on our searches of Medline and PubMed.Results: A total of 118 articles were included in the review, 16 of which exclusively addressed hypotheses about the role of Nrf2 on Glucose regulation, while 16 involved Cholesterol regulation. Likewise, 14 references were used to prove the importance of mitochondria on Nrf2. Multiple studies have provided evidence suggesting the involvement of Nrf2/HO-1 in various physiological processes, including metabolism and immune response. A total of 48 research articles and reviews have been used to highlight the role of metabolic syndrome and CVD.Conclusion: This review provides an overview of the literature on Nrf2/HO-1 and its role in metabolic disease syndrome and CVD.

Association between total bilirubin and bone mineral density level in adolescents

Background

Increasing bone mass accumulation in adolescence and obtaining greater peak bone mass is one of the effective methods to prevent osteoporosis in the future. We aimed to examine the association between total bilirubin and bone mineral density (BMD) level in adolescents.

Methods

We used the data from 2005–2010 and 2013–2014 cycles of National Health and Nutrition Examination Survey (NHANES). The BMD levels in the region of lumbar spine and femoral regions, including total femur, femoral neck, trochanter, and intertrochanter were measured. Univariable and multivariable linear regression model were used to assess the relationship between total bilirubin concentration and BMD.

Results

A total of 3741 participants aged 12–19 years were ultimately included in the study. There were 1997 (53.38%) males and 1744 (46.62%) females. Univariate analysis results showed that age, sex, race, education, income, body mass index, dietary calcium intake, and diabetes were correlated with BMD levels. Compared with the lowest quartile of total bilirubin concentration, the highest quartile of total bilirubin concentration was positively associated with BMD levels in the regions of total femur (β = 0.036, 95% CI = 0.021 to 0.050, P < 0.001), femur neck (β = 0.030, 95% CI = 0.016 to 0.044, P < 0.001), trochanter (β = 0.033, 95% CI = 0.019 to 0.046, P < 0.001), intertrochanter (β = 0.040, 95% CI = 0.023 to 0.056, P < 0.001), and lumbar spine (β = 0.032, 95% CI = 0.018 to 0.045, P < 0.001). We also observe the same trend in sensitivity analysis (P for trend < 0.001).

Conclusion

Our study demonstrated that total bilirubin concentration was positively associated with BMD levels in adolescents in United States. Total bilirubin concentration might be a protective marker against bone loss in adolescents.

Elevated serum bilirubin may significantly reduce coronary heart disease risk in females: A prospective cohort study

BACKGROUND AND AIMS

There is still inconsistent evidence over the protective effect of total bilirubin on the development of coronary heart disease (CHD). Therefore, we aimed to investigate the association between bilirubin in population subtypes and the risks of CHD between different gender and menstruation subgroups.

METHODS AND RESULTS

In this prospective cohort study, 29,750 participants free of CHD with an average age of 47 ± 14 years were recruited at baseline; of these, 720 CHD first-attack cases were collected after 7-years of follow up. The covariate-adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) of CHD with 95% confidence intervals (CIs). The serum bilirubin concentration was quarterly stratified based on the distribution of healthy population without CHD onset. The HRs of incident CHD decreased with elevated bilirubin in females (ρ trend<0.05), but not males. In postmenopausal females, compared with the lowest quartile of total bilirubin, the adjusted HRs for the third and fourth quartiles were 0.64 (95% CI: 0.45, 0.93) and 0.59 (95% CI: 0.42, 0.86), the adjusted HRs in the third and fourth quartiles of direct bilirubin were 0.56 (0.39, 0.82) and 0.56 (0.38, 0.81), and for indirect bilirubin, corresponding HR in the highest quartile was 0.56 (0.38, 0.83).

CONCLUSION

Elevated serum bilirubin was inversely associated with adjusted HRs of CHD in females, especially postmenopausal females. The relationship between elevated direct bilirubin and reduced HRs of CHD may be closer than indirect bilirubin in postmenopausal females.

Association of Triglyceride-Glucose Index and Liver Function Parameters Among Healthy Obese Civil Servants: A Center-Based Study

PURPOSE

To investigate the correlation between Triglyceride-glucose (TyG) index and liver function parameters in healthy obese civil servants in Shijiazhuang, China.

MATERIALS AND METHODS

This was an outpatient-based cross-sectional study in which 6452 participants were recruited. A total of 784 participants were analyzed according to inclusion and exclusion criteria. A TyG index was calculated based on fasting glucose and triglycerides. All patients were divided into a high TyG index group and a low TyG index group, using the median TyG index as a cut-off. Finally, patients were further divided into two subgroups: males and females.

RESULTS

While AST/ALT and direct bilirubin levels were lower in the high TyG index group compared to the low TyG index group, ALT, AST, total protein, and albumin levels were greater. Particularly in male participants, TyG index was inversely connected with AST/ALT and direct bilirubin levels and favorably correlated with ALT, AST, total protein, and albumin levels. These connections persisted in the multilinear regression study even after adjusting for confounding variables.

CONCLUSION

This study describes the correlation between TyG index and liver function parameters in obese populations without co-morbid diseases, providing a new idea for early interventional treatment in this group.

Heme-oxygenase and lipid mediators in obesity and associated cardiometabolic diseases: Therapeutic implications

Obesity-mediated metabolic syndrome remains the leading cause of death worldwide. Among many potential targets for pharmacological intervention, a promising strategy involves the heme oxygenase (HO) system, specifically its inducible form, HO-1. This review collects and updates much of the current knowledge relevant to pharmacology and clinical medicine concerning HO-1 in metabolic diseases and its effect on lipid metabolism. HO-1 has pleotropic effects that collectively reduce inflammation, while increasing vasodilation and insulin and leptin sensitivity. Recent reports indicate that HO-1 with its antioxidants via the effect of bilirubin increases formation of biologically active lipid metabolites such as epoxyeicosatrienoic acid (EET), omega-3 and other polyunsaturated fatty acids (PUFAs). Similarly, HO-1and bilirubin are potential therapeutic targets in the treatment of fat-induced liver diseases. HO-1-mediated upregulation of EET is capable not only of reversing endothelial dysfunction and hypertension, but also of reversing cardiac remodeling, a hallmark of the metabolic syndrome. This process involves browning of white fat tissue (i.e. formation of healthy adipocytes) and reduced lipotoxicity, which otherwise will be toxic to the heart. More importantly, this review examines the activity of EET in biological systems and a series of pathways that explain its mechanism of action and discusses how these might be exploited for potential therapeutic use. We also discuss the link between cardiac ectopic fat deposition and cardiac function in humans, which is similar to that described in obese mice and is regulated by HO-1-EET-PGC1α signaling, a potent negative regulator of the inflammatory adipokine NOV.

Small dense low-density lipoprotein-lowering agents

Metabolic disorders, including obesity, diabetes, and hyperlipidemia, as well as cardiovascular diseases (CVD), particularly atherosclerosis, are still leading causes of death worldwide. Plasma levels of low-density lipoprotein (LDL) are currently being considered as a critical risk factor for the diseases mentioned above, especially atherosclerosis. Because of the heterogeneous nature of LDL, many studies have already been conducted on its subclasses, especially small dense LDL (sdLDL). According to available evidence, sdLDL levels can be considered as an ideal alternative to LDL levels for monitoring CVD and early diagnosis of atherosclerosis. Recently, several researchers have focused on factors that are able to decrease sdLDL levels and improve health quality. Therefore, the purpose of this study is to describe the production process of sdLDL particles and review the effects of pharmaceutical and dietary agents as well as lifestyle on sdLDL plasma levels. In brief, their mechanisms of action are discussed. Apparently, cholesterol and LDL-lowering compounds are also effective in the reduction of sdLDL levels. In addition, improving lipid profile, especially the reduction of triglyceride levels, appropriate regimen, and lifestyle can decrease sdLDL levels. Therefore, all the aforementioned parameters should be taken into consideration simultaneously in sdLDL levels reducing strategies.

Bilirubin as a metabolic hormone: the physiological relevance of low levels

Recent research on bilirubin, a historically well-known waste product of heme catabolism, suggests an entirely new function as a metabolic hormone that drives gene transcription by nuclear receptors. Studies are now revealing that low plasma bilirubin levels, defined as "hypobilirubinemia," are a possible new pathology analogous to the other end of the spectrum of extreme hyperbilirubinemia seen in patients with jaundice and liver dysfunction. Hypobilirubinemia is most commonly seen in patients with metabolic dysfunction, which may lead to cardiovascular complications and possibly stroke. We address the clinical significance of low bilirubin levels. A better understanding of bilirubin's hormonal function may explain why hypobilirubinemia might be deleterious. We present mechanisms by which bilirubin may be protective at mildly elevated levels and research directions that could generate treatment possibilities for patients with hypobilirubinemia, such as targeting of pathways that regulate its production or turnover or the newly designed bilirubin nanoparticles. Our review here calls for a shift in the perspective of an old molecule that could benefit millions of patients with hypobilirubinemia.

Systematic Influence of Circulating Bilirubin Levels on Osteoporosis

Observational studies report some association between circulating bilirubin levels and osteoporosis, but it is unknown if this association is causal or confounded. In this two-sample Mendelian randomization (MR) study, we included a large genome-wide association study (GWAS) associated with total bilirubin levels among 317,639 people, a large meta-analysis to identify genetic variants associated with bone mineral density (BMD) estimated by heel quantitative ultrasound (eBMD) among 426,824 individuals and fracture among 1.2 million individuals. The results revealed that circulating bilirubin levels had no causal influence on eBMD (beta-estimate: 0.004, 95% confidence interval [CI]: -0.019 to 0.028, SE:0.012, P-value=0.705) or the risk of fracture (beta-estimate: -0.009, 95% CI: -0.035 to 0.017, SE:0.013, P-value=0.488), which were both confirmed by multiple sensitivity analyses. Our results confirm that circulating bilirubin levels have no causal role in eBMD or the incidence of fracture, indicating that circulating bilirubin levels is unlikely to be a causal risk factor for osteoporosis or fracture.

Sample Preparation Methods for Lipidomics Approaches Used in Studies of Obesity

Obesity is associated with alterations in the composition and amounts of lipids. Lipids have over 1.7 million representatives. Most lipid groups differ in composition, properties and chemical structure. These small molecules control various metabolic pathways, determine the metabolism of other compounds and are substrates for the syntheses of different derivatives. Recently, lipidomics has become an important branch of medical/clinical sciences similar to proteomics and genomics. Due to the much higher lipid accumulation in obese patients and many alterations in the compositions of various groups of lipids, the methods used for sample preparations for lipidomic studies of samples from obese subjects sometimes have to be modified. Appropriate sample preparation methods allow for the identification of a wide range of analytes by advanced analytical methods, including mass spectrometry. This is especially the case in studies with obese subjects, as the amounts of some lipids are much higher, others are present in trace amounts, and obese subjects have some specific alterations of the lipid profile. As a result, it is best to use a method previously tested on samples from obese subjects. However, most of these methods can be also used in healthy, nonobese subjects or patients with other dyslipidemias. This review is an overview of sample preparation methods for analysis as one of the major critical steps in the overall analytical procedure.

Associations between different bilirubin subtypes and diabetic microvascular complications in middle-aged and elderly individuals

AIMS

Some studies have reported associations between bilirubin and diabetic microvascular complications. However, these studies focused only on total bilirubin (TBIL) without distinguishing different bilirubin subtypes. In this study, we aimed to investigate the associations of TBIL, direct bilirubin (DBIL) and indirect bilirubin (IBIL) levels with albuminuria/creatinine ratio (ACR) and the prevalence of diabetic retinopathy (DR) among diabetic adults.

METHODS

We analyzed 4368 individuals out of 4813 diabetic participants enrolled from seven communities in 2018 in a cross-sectional study. Participants underwent several checkups, including the measurement of anthropometric parameters, blood pressure, glucose, lipid profile, TBIL, DBIL, IBIL and ACR. DR was detected by high-quality fundus photographs and was remotely read by ophthalmologists.

RESULTS

Compared with the first quartile of DBIL, participants in the fourth quartile had a lower prevalence of high ACR (odds ratio (OR) 0.76; 95% confidence interval (CI) 0.59, 0.99) (p for trend < 0.05). Neither TBIL nor IBIL was associated with the prevalence of high ACR. In DR, higher DBIL and TBIL by one standard deviation was associated with a 19% (OR 0.81; 95% CI 0.69, 0.94) and a 12% (OR 0.88; 95% CI 0.78, 0.99) lower frequency of DR, respectively (both p for trend < 0.05). However, IBIL was not associated with the prevalence of DR. These associations were adjusted for potential confounding factors.

CONCLUSION

DBIL had a stronger association with high ACR and DR than TBIL or IBIL did in diabetic adults. The effect of DBIL on diabetic complications should be noted and investigated in further studies.